The striker is retiring at the age of 38 and did so with the winning half-volley when beating Novara 2-1.
"There are no words. I trained hard yesterday despite the fact today was going to be a celebration and I prepared for this goal," said SuperPippo.
"With this jersey I have scored 300 goals and made 300 appearances in this stadium, in front of my people.
"It is a wonderful sensation. I feel good and it is difficult to leave. Playing somewhere that isn't Milan is also a tough idea to swallow, so I'll take a few days to decide.
"I will certainly come back here to Milan, because there is such a great love binding us that it cannot end today."